Compaction machines are frequently employed for compacting fresh laid asphalt, dirt, gravel, and other materials associated with laying road surfaces. One such type of compaction machine is a drum-type compactor having one or more drums adapted to compact particular materials over which the compactor is being driven. In order to compact the material, a drum-type compactor includes a drum assembly having a vibratory mechanism that typically includes multiple eccentric weights arranged about a rotatable shaft situated within a cavity of the drum. Both vibratory amplitude and frequency can be adjusted to establish a desired degree of compaction for the given type of material being compacted. In some conventional drum-type compactors for instance, the rotational speed of the eccentric weights may be adjusted to vary vibratory frequency, while the relative positions of the weights may be adjusted to vary vibratory amplitude.
While conventional vibratory mechanisms may provide adequate results, there is still room for improvement. In particular, in order to enable adjustable vibratory frequency and amplitude, conventional vibratory mechanisms commonly rely on multiple eccentric weights. However, manipulating a larger number of eccentric weights translates into larger magnitudes of inertia to overcome during operation. More specifically, more energy and/or time is typically needed to adequately startup and/or adjust the eccentric weights and achieve the desired vibratory frequency and amplitude. Furthermore, conventional systems rely a fairly complex arrangement of mechanical and/or hydraulic systems in order to drive the multiple eccentric weights and enable adjustability. Some conventional systems employ a single eccentric weight which may limit some of these adverse effects. However, these systems tend to be either limited in variability and/or dependent on rather complex mechanisms in order to provide variability.
One such example is disclosed in U.S. Pat. No. 4,759,659 (“Copie”). Copie discloses a vibratory drum compactor which uses a single eccentric weight that is movable relative to a central shaft of the drum compactor. Copie adjusts vibratory frequency by controlling the rotation of the shaft, and adjusts vibratory amplitude by controlling the position of the weight relative to the central shaft. In order to achieve this variability, however, Copie relies on an elaborate hydraulic network which pulls the weight inward when pressurized, and allows centrifugal force to extend the weight outward when not pressurized. Still further, the drum compactor in Copie is only capable of two discrete settings and thus limited in variability. More specifically, Copie operates in either a maximum vibration setting which extends the weight to its fully extended position, or a zero vibration setting which restores the weight to its fully retracted or centered position.
The present disclosure is directed at addressing one or more of the deficiencies and disadvantages set forth above. However, it should be appreciated that the solution of any particular problem is not a limitation on the scope of this disclosure or of the attached claims except to the extent expressly noted.